<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        div{
            border:1px solid salmon;
        }
        .clearfix::after{
            content: '';
            display: block;
            clear: both;
        }
        .wrapper1{
            width: 500px;
            margin-bottom: 100px;
        }
        .wrapper1>div{
            float: left;
            height: 50px;
        }
        .wrapper1>div:first-child{
            margin-right: 30px;
        }

        .wrapper2{
            width: 600px;
            margin-bottom: 100px;
        }
        .wrapper2>div:first-child{
            float: left;
        }
        .wrapper2>div{
            float: right;
        }
        .wrapper3{
            width: 600px;
            margin-bottom: 100px;
        }
        .wrapper3>div:first-child{
            float: left;
        }
        .wrapper3>div:nth-child(2){
            width: 200px;
        }
        .wrapper3>div:nth-child(3){
            float: right;
        }
    </style>
</head>
<body>
    <!-- 左右布局 -->
    <div class="wrapper1 clearfix">
        <div>the first div element</div>
        <div>the second div element</div>
    </div>

    <!-- 左中右布局 -->
    <div class="wrapper2 clearfix">
        <div>the first div element</div>
        <div>the second div element</div>
        <div>the third div element</div>
    </div>
    <!-- 尚未实现的效果 -->
    <!-- <div class="wrapper3 clearfix">
        <div>the first div element</div>
        <div>Lorem ipsum dolor, sit amet consectetur adipisicing elit. Quam eum minima commodi saepe suscipit unde sit nihil est vitae voluptatibus eveniet reprehenderit id provident iste sequi delectus placeat, maiores sed.</div>
        <div>the third div element</div>
    </div> -->
    <div>
        我要垂直居中啊啊啊
    </div>
</body>
</html>